This invention relates generally to radio frequency antennas and more particularly to multibeam antennas adapted to operate over a relatively wide band of frequencies.
As is known in the art, an array antenna may be arranged so that it produces a plurality of simultaneously existing beams of radio frequency energy. One such antenna is described in U.S. Pat. No. 3,761,936, Multi-Beam Array Antenna, inventors Donald H. Archer, Robert P. Pricket and Curtis P. Hartwig, issued Sept. 25, 1973 and assigned to the same assignee as the present invention. As described therein, the array antenna is adapted to produce a plurality of simultaneously existing beams of radio frequency energy, each one thereof having the gain and bandwidth of the entire aperture. Such array antenna has a wide range of applications, such as in a relay or transponder as described in U.S. Pat. No. 3,715,749, Multi-Beam Radio Frequency System, inventor Donald H. Archer, issued Feb. 6, 1973, and assigned to the same assignee as the present invention. As described therein, in one application a pair of multi-beam array antenna is used; one for reception, and one for transmission. Radio frequency energy along a particular wavefront is formed to a particular output port of the array, detected, fed to a corresponding input port of the transmitting array and retransmitted back along the same direction as the received wavefront. In many applications of such type, it is frequently desired that the antenna system operate over a relatively wide band of frequencies.